Electrical transmission system



' 2 Sheets-.Sheet 2 H. NYQuas-r ELECTRICAL TRANSMIS S ION SYSTEM Filed may 1g. 1945 Ml. Q 6i" l /NVE/vmR hf /VYQU/ST BV ATTORNEY Patented` ug. '5, 1947 UNITED smrss PATENT or' c ELECTRICALTRLNSMISSION SYSTEM Harry .'Nyquist; Millburn, N. J., assigner to( Bell Telephone. Laboratories; Incorporated, New

York, N. Y., a corporation of New York Application May 10,1945, Serial No. 592,968

6 Claimsa I The present invention relates tocircuits or -ap'- paratus for closing con-troll paths from; any one of a number of input leads or terminals to` any" one of a number of output leads or terminals ona permutation'- basis. The circuits for performing this functionare`V termed permuters.

While the invention is capable of gener-ai application it. will' be illustrated! in connectionv witha secret transmission or control' system; by Wayof specic example. In'- such a system` it may be supposed that'` a number N of devices at' the receiving end of thesystem-are to lieV actuatedf individually by means of N controllers placed` at` the transmitting end of the system. Any type of transmission systemmay be visualized betweenkk theA controllers and the devices, the siinplesty consisting, of' course, of' Nl separate conductors leading individua-llyf'romthe controllers to the respective devices. Any suitable type of multiplex transmissionl can be usedf in practice vbuttlie N- conductors w-illl be assumed as physical ly present atv the transmitter and again' atV theVVA receiver.

If a permuter be inserted in these Ni' conclue torsatithetransmitter and anA identical permu-ter be inserted similarly at the receiver and properly' connected inx circuit, secrecy in transmission can be obtained overthe intervening` transmission system, of Whatever type, provided the permuters are operated? so as to avoid any recognizable rule or scheme of interconnection of control' paths between the input and output leads of; the permuter. Ideally a voltage impressed on anygiverll input lead of the permuter should have an equal chance of energizing any output lead, regardless of the previous history of the interconnections usedl. Tapping any one`- or allf of the' N transfmission` lines or channels will under these condi-- tions giveno clue tothe particular controllers that are being actuated. Correct control is exe erted at the receiver, however, since the control paths there pass through the second permuter which is identical to the rst in mode of operation.

It is the general object; oi' the inventionn to provide for alli possible permutations between a given group-ofinput leads anda similar group of output leads without the use of excessive equipment.

A further andmore specificA object oi the in illustrative embodiment shown in the attacheddrawings in which:`

Fig. I shows i'n diagrammatic outline form a transmitting station for a teledynamic system according to. theI invention;

Fig. 2* is a similar showing of the receiver for such a system;` and' Y Fig. '3 shows the wiring Adiagram in detaill for a permuter of al type suitable' for use, for example, inf the systemv of Figs. 1 and 2.

Referring -rst to- Fig. 3, a 4 X 4' permuter is shown comprising four input leads at the left labels Mr, M2; Mi and and four output leads at the rightl labeled S1', Se, S3 and S4. The input4V lead'smay', for example, beconsidered as message leadsl for impressing volta-ges havingv` a certain message* content and the output leads may be thought ofA as signal transmission leads for conveying the coded information further along inthesystem. y

The l'ead Mi' passesV in series' through the left# hand` windings of' four double-woundv relays shownat Ifll, H5, F2 and- [-3. A similar arrangement of Wiring is provid-ed forl they leads Mz, Ms

In` order( tc operate' the relays, circuits are pro vided=` for passing'cu'rrents also throughA thev righthand w-ihdingslf-romf the four respective leads Kr, K2; K3L andi Kir. These" voltages are key voltages which for purposes of the system shown in Figs. 1 andi Z-lare made to occur ina'higlily irregular ordei oneC at alV time on* theV four K-leads. I- a voltagev appears' simultaneouslyonone'- of the M-leadsl and one'oftheKS-l'eads; one cnly'oi t-he sixteen relays in Fig. 3 will respond since this is the onlyl' relay! which willi have current flowingin botl'i'l ofiits windings'.-

lf avoltage appears! simultaneously `on lead Mi and le ad K4; the relay5 l3- will attract its arma-ture andA applyy voltage-'from battery 23% tol output lead`V Vl/henever relay I3 is energized; therefore;

Si. output lead Si is actuated' and the characterV Si is shown adjacent" relay' r3 to. indicate this' factl It will be notedthat each output or 1S lead is wire@V Ml S4 Sz S2 S1 M2 S3 Sz Si S4 M3 S3 S1 S4 S3 Y M4 Si S4 Ss Sz K1 K2 K3 K4 It will be Ynoted from this table that any input l lead can exert control over any output lead depending upon the K-conductor that is energized. This table also illustrates the'fact that with lonly sixteen intersecting points arranged as in Fig. V3 only four of the possible twenty-four permutations can be obtained, these four being represented by the four vertical S columns.

Referring now to Fig. l, six controllers in the form of switches or keys are shown at 3| to 36, there being no special signicance to the number six. These keys are intended to be pressed one at a time or tWo or more of them may be pressed simultaneously. When any key is pressed and closes its operate contact, pulses of current are sent from battery 40 through rotary contact maker 4| and brush 42 over the corresponding input lead or M-lead, Mi to Ms. The interrupter 4| rotates at a constant speed and may be arf ranged to close the circuit for any desirable fraction of a rotation, such as a quarter of a rotation, for example. The M-leads are wired to a cross-connecting panel 45 which permits the six input terminals to be cross-connected in any desired order to the six output terminals by means of patching plugs or otherwise. These cross-connections may be changed manually at stated times, such as once a day or once per mission of a directively controlled device in accordance with a prearranged schedule or program. Y

In accordance with the present'invention, assuming a six-conductor system, ve permuters are used comprising a 2 x 2 permuter shown at 4S for any two, such as the lowermost two, rnessage leads; a 3 x 3 permuter 4'! for the two output leads from permuter 45 plus one of the other message leads; a 4 x 4 permuter 48 for the three output leads of permuter 4l plus another one of the message leads; a 5 x 5 permuter 49 similarly arranged; and, finally, a 6 x 6 permuter 5U. These five permuters are capable of giving all possible permutations between the leads M1 to M6 and theV output leads S1 to Se.

The K-voltages could be pro-vided to these permuters in any desired manner, two such voltages being required for permuter 46, three voltages for permuter 47 and so on up to six voltages for permuter 50.

In a secrecy system it is desirable that the K- voltages be applied in a highly irregular and in as nearly a random order 0f occurrence as possible the transmitting and receiving stations. These '(5 punched tapes are shown at 5|, 52, 53, 54 and 55 as passing over a continuously rotating roller 56 which may be geared to the circuit interrupter 4| so as to be driven from the same motor with a proper speed relation. The roller 55 moves the ve tapes at uniform speed across bedplate 5l' which is maintained at a positive voltage by means of batteryg58. Sets of brushes are arranged above the bedplate -51 to make Contact therewith whenever a hole appears in the tape beneath a given brush. At the instant shown in Fig. 1, voltage from the battery 58 is being applied through a perforation in tape 5| to the right-hand brush leading to the right-hand K- conductor K2 of permuter 45. Also the middle brush 0f tape y52 is applying a voltage to the middle K-lead of permuter `4'| and the second brush from the left in the Vcase of tape 53 is applying voltage to a second K-lead of permuter 48 and so on. By arranging the holes in the tapes in an irregular manner, the application of the voltage pulses to the K-leads of the various` permuters canl be made in as highly irregular-order as desired. The rate of movement of the tapes in relation to the drum 4| should be such that drum 4| closes the circuit for an interval and then opens the circuit while a brush is in contact with' the bedplate 51 through a corresponding tape perforation. This insures that a voltage is always on a K-lead at the time when a pulse is applied to an M-lead and remains on the K-lead until the end of the corresponding pulse as measured by the interrupter 4|.

The voltages appearing on the output leads S1 to Se are transmitted by individual line wire conductors or by multiplex transmission, for example on a carrier basis, over a line or radio channel or in any other manner to` the station in Fig. 2, the incoming leads at the latter station being similarly labeled at the left. In Fig. 2, five permuters are used which are duplicates of those at the transmitter and are similarly designated by reference numerals. Also a similar cross-connecting Yframe or panel 45 is used. It will be noted that in Fig. 2 these six items appear in a reverse order from left to right with respect to the corresponding items in Fig. 1. Five duplicate tapes 5| to 55 are provided at the receiver and are driven by roller 56 in exact synchronism with the five tapes at the transmitter. This insures that K-voltages are supplied to the permuters at the receiving point at the same instants as at the transmitter and to analogous- K-leads.

In order properly to decipher the signals it is necessary to connect the armatures o f the receiving permuter relays in proper groups `to the'outgoing conductors. Arranging the S-leads as the incomingV leads and the M-leads as outgoing, the manner of wiring the relay output circuits is indiappearing in thetable indicate which relay outputs are -tofbe connected in parallel to the correspondingly-v numbered M-lead. Thus, if the incoming voltage is on lead S3 and the key `is Kg. the upper or M1 output lead is chosen. Referring to Fig. 3 or to the previous table, when M1 and K2 were usedin coding, lead Ss-was actuated. Thus M1 is recovered by decoding S3 with the same key element K2.

Analogous to the above tables, the tables for a 3 X 3 and for a 6 x 6 permuter would be as follows:

M1 3 2 1 Si K1 K2 K3 M1 6 5 4 3 2 1 S1 N12 5 4 3 2 l 6 S2 M3 4 3 2 l 6 5 Ss M4 3 2 1 6 5 4 S4 lvl; 2 1 6 5 4 3 S5 Mc 1 6 5 4 3 2 Sn K1 K2 Ka K4 K5 Ku It is not necessary that the arrangement be a symmetric one and by Way of illustration the following asymmetric diagram is given for a 5 x 5 permuter. It will be no-ted that the interval M1 2 5 3 4 1 S1 5 4 3 2 1 im 5 3 4 1 2 s2 1 5 4 3 2 M5 3 4 1 2 5 s3 a 2 1 5 4 M1 4 1 2 5 3 s1 4 s 2 1 5 M5 1 2 5 3 4 S5 2 1 5 4 3 K1 K2 K3 K4 K5 K1 K2 K3 K4 K5 relay attracts its armature and closes an operating.

circuit from battery 59 over the armature and front contact of the corresponding relay to whatever work circuit may be desired. By way of example, the upper two relays R1 and R2 may control a right and left rudder; the second pair of relays R3 and R4 may control an up and dowln elevator VWhile the next pair of relays R5 and Re may control a starting and stopping circuit or other actuating or control circuits. In this type of embodiment the six relays may be made, therefore, to control a dirigible body, such as an airplane, torpedo or the like. In such a system the relays R5 and Re may instead, by way of further example, control the release or iiring of a charge or perform a similar operation.

In the operation of the system, according to Figs. 1 and 2, key 3l when pressed will cause the transmission of impulses to the winding of the relay R1 and cause that relay to attract its armature. The arrangement may be such that the relay R1 holds its armature attracted as long as the key 3l is closed. This may be done by use of a holding circuit including a condenser and resistance in the circuit of the relay or otherwise in accordance with known practice. Similarly, whenever key 32 is depressed relay R2 is actuated and so on, each key individually controlling its corresponding relay.

Any one listening in on the system between the sending and receiving stations would, however, be unable tc perceive which types of control are being sent over the system since the pulses are being continuously permuted over the six S-con'ductors in Yan unintelligible manner. this'reason also it Vwill be impossible vfor an unauthorized personr to `directively control the receiver because he could not know at any instant what pulses must be sent over any of the channels S1 to Ss in order to effect a given typeof response at the receiver. It is necessary in order to decode theV signals to have possession of a receiving station according to Fig..2 and also a set of key tapes identical with those in use at the transmitter. It

is also necessary to know the character of crossconnections made in panel 45 at the transmitter.

It will be understood that the choice of six conductors instead of some other number has been merely by way of example and that the principles disclosed are equally applicable to systems of either greater or less number of conductors or signal elements or values.

What is claimed is:

1. In combination in an electrical circuit, a group of N separate input conductors and a group of N separate output conductors, where N is an integral number greater than 3, and means to establish simultaneous individual circuit connections between said input and output conductors respectively and to permute said circuit connections among themselves comprising a succession of N-l permuters each embracing a different fractional number of said circuit connections from two to N such circuit connections respectively.

2. In combination in an electrical circuit, a group of N separate input conductors and a group of N separate output conductors, Where N is an integral number greater than 3, and means to extend individual control paths simultaneously from said input to said output conductors, respectively, and to permute said control paths among themselves comprising a succession of N-l permuter circuits, one of which embraces two only of said control paths, and others increasing in size and embracing successively one more of said control paths up to the largest one which embraces all N control paths.

3. In combination in an electrical circuit, a

group of N separate input conductors and a group of N separate output conductors, where N is an integral number greater than 3, and means to extend individual control paths from said input conductors to said output conductors and to permute said control paths among themselves comprising N-l permuter circuits for successively permuting groups of said control circuits varying in size by one additional control circuit from two to N control circuits.

4. An electrical circuit according to claim 3, each permuter having individual input leads and individual output leads, and means to extend a control path from any input lead to any output ead.

5. An electrical circuit according to claim 3, each permuter having individual input leads and individual output leads, and means to extend a control path from any input lead to any output lead, comprising a group of key leads forming intersecting points with said input leads, means at said intersecting points for exerting controls over said output leads, and means to apply key voltages to said individual key leads to control actuation of said control exerting means.

6. In a signaling system, more than three separate signal input circuits, a corresponding number of output circuits, means to exert controls upon individual output leads from individual signal input leads, including means to exert control upon two intermediate leads from two of said sig- Y nal input circuits in accordance with one key, REFERENCES CITED means to exert Control upon three other meer* The following references are of record in the mediate leads from said two intermediate leads me of and a third one of said signal input circuits in 5 uns patent' accordance with another key, and means to exert UNITED STATES PATENTS control upon said output leads from the last vNumber Name Date group of intermediate leads and the last of said 2,139,676 Friedman Dea 13 1938 signal input leads in accordance withanother key.

HARRY NYQUIST. 

